Fall is Coming

Meteorologically speaking, autumn began on Sept., 1 but the autumnal equinox marks the astronomical start to the fall season.

This year, the baton is passed from summer to fall (in the Northern Hemisphere) on Monday, Sept. 22, at 10:29 p.m. EDT.

So what exactly happens during this time?

Twice a year, around March 20 or 21 and Sept. 22 or 23, the sun's most direct rays shine over the Earth's equator. These two days are known as the March (vernal or spring in the Northern Hemisphere) equinox and the September (autumnal) equinox.

The specific time of 10:29 p.m. EDT marks the passage of direct sunlight over the equator from the Northern Hemisphere to the Southern Hemisphere.

http://www.weather.com/news/science/autumnal-equinox-first-day-fall-september-22-20140920